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On 05/18/2010 07:57 PM, Jan Engelhardt wrote: |
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> |
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> On Tuesday 2010-05-18 18:56, Stefan G. Weichinger wrote: |
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>> |
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>>>> Do you know any howto where it is done "the right way"? |
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>>> |
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>>> The right and easy way is to just use the supplied pmt-ehd(8) tool, |
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>>> which works both interactively and non-interactively, depending on |
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>>> whether it's called with enough arguments or not, so there's something |
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>>> for everybody's flavor. |
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>>> It does not do LUKS yet as of pam_mount 2.2, though. Guess my |
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>>> todo list gets longer.. |
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>> |
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>> :-) |
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>> |
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>> But given the fact that I store the key on the same hard-disk with the |
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>> shadowed user-pw I could also leave that openssl-part straight away, |
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>> correct?? seems the same level of (in)security to me ... |
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> |
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> Yes. The point of keyfiles is to be able to change the password on |
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> a volume. |
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> |
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> Without a keyfile, a crypto program would take the password, hash it |
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> somehow, and you get your AES key. Changing the password means having |
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> a different AES key, meaning decrypting the disk will yield a |
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> different result. In other words, changing the password would require |
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> at least reading the old data, reencrypting it and writing it again. |
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> Takes time. |
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> |
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> With a keyfile, you retain the same AES key all the time, and encrypt |
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> the AES key itself - reencrypting the AES key is quick, as it's |
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> only some xyz bits, not terabytes. |
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|
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That's not true for LUKS. This is one of the nice things about it: |
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Multiple keys can be used on a volume, and it is possible to change the |
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passwords in a safe way. (You have 8 "key slots", each can be used to |
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decrypt the volume. To change a PW use a new slot, then remove the old |
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one.) The trick here is that LUKS does by itself safely, what you are |
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trying to do with the SSL-key in a hackish way (no offense). The key |
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setup scheme is a modified TKS1 (nice Paper: |
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http://clemens.endorphin.org/TKS1-draft.pdf - read section 2 "Two Level |
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Encryption") which uses the keys in the key slots to encrypt a master |
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key which is used to encrypt the volume. So the only key(s) you ever |
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change is the key(s) encrypting the master key. |
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LUKS really does by itself already, what you are doing :) |
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So I'm pretty sure, that it is safer to use the LUKS key setup (that has |
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been peer-reviewed by security experts), than a self written shell script. |
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|
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Bye, |
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Daniel |
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-- |
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PGP key @ http://pgpkeys.pca.dfn.de/pks/lookup?search=0xBB9D4887&op=get |
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# gpg --recv-keys --keyserver hkp://subkeys.pgp.net 0xBB9D4887 |
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